How to design a mobile mechanism and how to control the mobile mechanism are important research issues in the field of mechanical engineering. Heretofore, there have been proposed mobile mechanisms that move by undulatory locomotion, such as a snake-like robot (see documents 1 and 2 in the document list presented below), a snake board (see document 3), a roller walker (see document 4) and a snake-like mobile robot (see document 5).
The aforementioned snake-like robot disclosed in documents 1 and 2 is constructed by joining a plurality of links on which passively turning wheels are attached. Movement of the snake-like robot is realized by driving joints between the links. The undulatory locomotion is a motion resulting from changes in the shape of a mobile mechanism, as is the case with the snake-like robot.
The aforementioned snake board (see document 3) has a rigid body having a moment of inertia that rotates about the center of gravity of the vehicle. In addition, it has passively turning front and rear wheels provided on the vehicle. Both the front and rear wheels are provided with a steering function. Movement of the snake board is realized by rotating the rigid body having a moment of inertia while operating the two steering mechanisms.
In the aforementioned roller walker (see document 4), passively turning wheels are attached at the ends of the legs of a four-legged robot, where its movement is realized by driving the joints of the legs.
The aforementioned three-branched snake-like mobile robot (see document 5) has a structure in which links on which passively turning wheels are attached, by means of joints, to the vertexes of a base having an equilateral triangle shape. The structure of this tree-branched snake-like mobile robot has been designed with a view to research specific properties of kinematic equations thereof. For this reason, although movement of the three-branched snake-like robot is realized by driving joints, its movement is intermittent unlike with the aforementioned snake-like robot, snake board and roller walker that can move smoothly, and improvement of the three branched snake-like robot is desired.
In order to realize stable operation of the snake-like robot, the snake board, the roller walker and the three-branched snake-like mobile robot, a closed loop control system, such as a feedback control system for realizing a target position and a target posture in an asymptotically stable way or a feedback control system for causing a mechanism to follow a straight or curved path (or a track) is required.
Heretofore, a feedback control system that causes a snake-like robot to follow a target track based on kinematic equations thereof has been proposed (see document 6). However, it is necessary to devise a feedback control system for causing not only snake-like robots but also other mobile mechanisms that perform undulatory locomotion to follow a target path (or a track).
(Document List)    [Document 1] Shigeo Hirose, “Seibutsu Kikai Kougaku” (Biomechanics), Kogyouchousakai Publishing Co. Ltd., (1987).    [Document 2] S. hirose, “Biologically Inspired Robots (Snake-like Locomotor and Manipulator)”, Oxford University Press, (1993).    [Document 3] J. P. Ostrowski and J. W. Burdick, “The Geometric Mechanics of Undulatory Robotic Locomotion”, International Journal of Robotics Research, vol. 17, no. 7, 683/701, (1998).    [Document 4] Shigeo Hirose and Hiroki Takeuchi, “Roller-Walker: A New Leg-Wheel Hybrid Mobile Robot”, Transactions of the Japan Society of Mechanical Engineers (C Ed.), vol. 62, no. 599, 2758/2764, (1996).    [Document 5] Yasushi Iwatani, Masato Ishikawa and Shinji Hara, “Analysis and Control of a Trident Snake-Like Mobile Robot”, Transactions of Instrument and Control Engineers, vol. 39, no. 12, 1159/1161, (2003).    [Document 6] Yoshikatsu Hoshi, Mitsuji Sampei and Masanobu Koga: “An Autonomous Locomotion Control of a Multi-Joint Snake-Like Robot with Consideration of the Dynamic Manipulability”, Journal of the Robotics Society of Japan, vol. 18, no. 8, 1133/1140, (2000)